使用父类时静态属性的问题:

When I run this code:

当我运行这段代码:

<?php
require_once 'getdata.class.php';
class Header extends GetData
{ 
    public $headers;

    public function sayfaHeader($sayfa = 1) 
    { 
        return parent::$sql = "SELECT * FROM header WHERE id='" . $sayfa . "'"; 
        //$data = parent::getData();
        return $data;
        $this->headers = (object) $data;
        return (object) $this->headers;
    } 
} 
$header = new Header;
echo $header->sayfaHeader();

?>
<?php
requi